Siftpkoofbag



Dec. 19, 1944. J 1 sHlVELY 2,365,651

SIFT PROOF BAG Filed Nov. 25, 1942 2 Sheets-Sheet l INVENTOR JAMES L. SHIVELY TORNEYS Dec. 19, 1944.

J. L. SHIVELY SIFT PROOF BAG Filed NOV. 25, 1942 2 Sheets-Sheet 2 I NVENTOR JAMES L. SHIVELY M d 1 I ATTORNEYS l atented Dec. 19, 1944 K UNITED STATES PATENT/OFFICE sn rraoor BAG James L. Shively. Oamas. Wash. assignor to Crown Zellerbach Corporation, San Francisco, Calii'., a corporation of Nevada Application November 25, 1942, Serial No. 466,932 3 Claims. (01. 93-35) This invention relates to the making of. paper other, or a separation of the plies, may occur bags 01' the satchel bottom and similar types, whenever a transverse told is made in the bag and, more particularly, to the making of bags tube in the forming and folding down of the of such types which are required to be sift-proof, bag bottom. This slippage may result subseas, for example, bags in which carbon black is 5 quently in the outer and inner laps at the seam packed. V parting very slightly, or it may result in one lap The object of my invention is to assurean abe n P e O m ch lighter n t e Other solutely leak-proof or sift-proof seam in the tube t at wh n th d i at stra h n d ut. up n from which the bag is made, the filling of the bag, a rupture of the edge of Heretofore there have been frequent com- One Of the Plies Will Occur at this P n plaints, o th part of persons handling carbon either case a leak develops in the filled bag as a black, that the paper bags in which such materesult vIn a m -Dly a he same situation rial is packed, often developed a small l ak in exists more or less in the seams oi all the plies th seam, causing pufis of black carbon to wherever failures occur, but of course the most expelled from the bag every time the bag is important Seem to be ep leakproof in a multihandled .or touched, and causing the carbon con- P bag is the seam 0f the Outer plies. t t gradually t leak Because of the I thus discovered'that practically all the imculiar nature of the carbon black in particular, a Perfeetiehs in the bag Seems, which produced very small failureof the bag seam is sufllcient leaks in the bags which caused a pture in to produce a serious leak when the bag is filled the b e seems which in turn oduced the leaks, t such materiaL were due to such displacement, disarrangement By closely observing the paper bags in whi h or separation of the lapped, pasted edges at some carbon black is packed where such leaks occur, Point along the seam Where a old had Occurred and after considerable experimenting in the during Completion of e a ottom. The making of such bags for the purpose of deterobject of my present invention consequently has mining the cause of the development of uch been to avoid the occurrence of Such imperfecleaks, I finally discovered that the difiiculty is 710113 in the Seamattributable to certain faults in the making of I have fmmdthat these dimeulties may be'sucthe bag whichIshall describe briefly. cesfuny Overcome and'prevented by cementing These bags are generally and preferably made bmder Strip P the bag tllbe Seam mediately the tube at the top of, the machine. Having the at Seam is Previously ceeted with a strong seam so located in the machine is an advantage adheslve 0f the type co11111101115 used on binder in-that it enables the operator to watch the initape E m tape- This adhesive consists of Paste is used in the forming of the bag tubing in 4 tube e m after h se m has e n p d. the

has not been found feasible, in bag-making ma- 1n the s m has not yet become dry. In carrying chines, to use a strong quick-drying glue instead out my method I fehm the b tube nd he pasted of such paste for forming the tube seam. Seam in the usual manner a d apply Strong I have discovered that, in the forming of the gummed tape, of a Width fll nt to extend some bag bottom the edges 01 the paper along the tube distance on each side of 15116 seam, 011 top Of the seam become displaced longitudinally to some seem, the adhesive o e tape ha ing first been extent at certain points where transverse folds rendered tecky- The e n r S rip is immeoccur, or may be separated from each other at i l pr d down firmly 0n the seam, and, if or near such points, due to the fact that the ner as a single sheet or unitary structure. In of the Seam n y he overlappe edges f th consequence. either a slippage 01' one ply on the m, ven though the paste in the seam has not yet dried, will not slip on each other during the folding of the tube, but the plies at the seam, together with the binder strip, will form a unitary structure and this structure will be preserved during the folding. Thus the primary purpose of the applied binder strip is to hold the seam tight durin the folding and until such tim as the paste in the seam is thoroughly dry. The effect of this application with the binder strip along the bag seam can be explained more fully with reference to the accompanying drawings. in which:

Fig. 1 is a perspective view of a section of paper bag tubing ready for the bottom-forming operation, the seam in the bag tubing having been formed in accordance with my invention;

Fig. 2 is a fragmentary view, in perspective, of an end of the bag tubing showing more clearly th improved manner of forming the seam;

Fig. 3 illustrates the paper bag tubing of Fig. 1 during one stage in the forming of the bag bottom;

Fig. 4 shows the completed bag with the bottom entirely formed;

Fig. 4A shows the bottom portion of an ordinary completed;bag in which the seam has been formed merely in the conventional manner;

Figs. 5 and 5A are diagrammatic views illustrating the effects produced by the transverse folds at the bag seam of an ordinary bag in the forming of the bottom;

- Fig. 6 is a ordinary bag in use showing the resulting leakage points; and

Fig. 7 is a diagrammatic elevation of an appa ratus adapted. to carry out my invention on a conventional bag-forming machine.

Referring first to Figs. 1 and 2, the bag tubing I3 is formed on a bag-makin machine in the conventional manner which includes the lapping of one longitudinal edge ll of the sheet over the other longitudinal edge l2 and the securing of the two overlapped edges together by a film of paste between them. As previously explained,

this paste requires considerable time in which to dry, and it has not been found feasible in bag machines to substitute other adhesive means in place of the usual paste.

Immediately upon forming of the seam in the conventional manner I apply a strip of gummed tape l0, constituting a seam binder strip, over the entire seam. This binder strip, or gummed tape, is preferably made of heavy paper, or similar suitable material, one face of which carries a coating of glue which the application of the binder strip to the seam the glue is moistened. This renders the glue tacky so that the binder strip will then adhere very strongly to any surface with which its gluetreated ars comes into contact. However, after such mcistening, the glue again dries very quickly, and consequently the binder strip must immediately be applied to the seam. The width of the binder strip l0 must be sufficient to enable the strip to extend a distance on each side of the seam (as shown in Fig. 2) to enable the binder strip to have a firm hold on both plies adjoining the seam. The result is held so strongly in place that the subsequent manipulation and folding of the tube, which takes place in the forming of the bag bottom, will not cause the overlapped edges II and I2 of the seam to slide one upon the other, or separate, even though the film of paste between them has not yet dried.

has been dried. Prior to that the two plies will be fragmentary side elevation of an In Fig. 3 the bag bottom is shown in the process of formation at one end of the section of the bag tube. This figure illustrates the forming of what is commonly known as a satchel type of bag bottom. A transverse fold has been made across the seam of the tubing on the line H. Subsequent transverse folding also takes place On the lines 15 and 16 in the forming of the bottom, the fold on the line 15 also being made across the seam. When paste has been applied to the bottom flaps l1 and I8 and these flaps are folded, on over the other, the forming of the ba has been completed. Fig. 4 shows the bag finished and now ready for use. In order to explain more clearly how the particular problem, with which my invention is concerned, arises, I shall describe briefly what occurs when a similar bag bottom is formed on bag tubing when my invention is not used. Fig. 4A shows the corresponding bottom of an ordinary bag having the usual seam IS in the bag tubing, and showing the bottom as formed in exactly the same manner as in the bag of Fig. 4. The transverse folds Ha, 15a and l8a correspond to the folds l4, I5 and I6 respectively in Figs. 3 and 4. In Figs. 5 and 5A the two overlapping edges of the bag tubing material at the seam of the bag (constituting the seam 19 in Fig. 4A) are designated by the reference characters 20 and 2|, and the film of paste between the overlapping edges at the seam is indicated by the heavy line 22. When the transverse fold Ha is made across the bag seam, assuming that the paste film 22 has not yet entirely set" or dried, there will be a tendency for the lap 2| to slide slightly with respect to the lap 20 in either or both of the directions indicated by the arrows a: and :1," and approximately at the places I where these arrows are shown. Similarly when tendency will be the next fold l5a is made, the for the lap 20 to slide with respect to the lap 2| as indicated by the arrows y and 1/. If the two overlapping edges were entirely free to slide at all points with respect to each other, the opposite tendencies and motions indicated at a: and y might compensate each other. However, upon the subsequent straightening out of the folds the tendencies would be reversed. To a modified degree this is what might occur if the paste film in between offered no resistance. The paste film however does offer some resistance and the amount of resistance will depend largely upon the extent to which the paste has become set. If the paste were entirely set before any folding took place the paste film would presumably be strong enough to hold the overlapping edges firmly together and prevent any longitudinal will be only slight or partly set when the folding occurs. The tendency of the lapped edges to move with respect to each other may be sufficient to break the partly set paste film in which case a weakened paste line will result. On the other hand, if the past film is partly set the previously-described tendencies may only force the adjacent laps slightly apart at certain points, such as those indicated at z in Fig. 5A.

The effect of these weaknesses, either total or partial failures, in the pasteseatm, will be appreciated with reference to Fig. 6 in which an ordinary bag 23 having such defects in the seam is assumed to have been filled with a substance such as carbon black. In the bag 23 the broken line 24 indicates the original lfold line I 4a of Figs. and 5A, while the bottom edge line 25 corresponds to the fold line |5a of Figs. 5 and 5A. Not only will leaks occur on or near these fold lines but I have also discovered that when a heavy strain is placed on the bag, since one of the lapped edges is pulled tighter than the other at the fold line, the more tightly stretched edge of the material will tear apart, as illustrated at 26, whereupon the failure of the bag becomes even mor serious. The rupture 26 has been somewhat exaggerated in Fig. 6 for the purpose of illustration.

With the use of my invention, as previously explained, the tendency of the ovrlappod edges of the seam to slip with respect to each other, or to separate at points on or adjacent the fold lines, is successfully resisted, since the gummed tape. or binder strip, holds the two edges of the material firmly together at the seam until the paste film is entirely set. Although the binder strip then remains attached to the bag tubing, and to some extent continues to be a reinforcing for the bag, its real purpose is accomplished as soon as the paste seam has entirely set, for presumably the film of paste itself would then provide a sumcient hold to prevent an leak occurring, along the seam.

In Fig. 7 I have indicated a simple and practical apparatus which has been successfully employed, in combination with a well-known type of bag-forming machine, for carrying out my inflgure the bag tubing 21, which been formed in th usual manner with the pasted seam at the top of the anachine, is moving in the direction indicated by the arrow. A roll of gummed tape 28 is mounted on the machine above the bag tubing and in line with the seam includes means for moistening the glue on the gummed tape. After leaving the gummed tape passes under a guide pulley 3| and finally becomes attached along the seam of the bag tubing, as the tubing and binder strip are together drawn between a pair of draw rolls 32. After the binder strip has thus been firmly attached to the bag tubing along the seam, the bag tubing is cut into the desired lengths for the bags in the usual manner, by a chain or knife cutoff 33. From this point on the formation of the bag continues in the usual manner.

I claim:

1. In the making of a bag of the character described having a longitudinal seam and a bag bottom folded over on the seam, the improved method of forming the longitudinal seam and of the dispenser 30,

preventing failure in the same without delaying the completion of the bag, said method comprising arranging the 'bag material so that the bag material become momentarily tacky and then quickly set bag tubing so that 3 said binder strip firmly against said surface, and forming the bag bottom without waiting for said slower-drying film of paste between said overlapped edges of said bag material to set," whereby said binder strip will cause said overlapping edges to act as a unitary structure during the folding of the bag bottom and prevent any movement of one edge with respect to the other pending the permanent setting of said slowerdrying film of paste.

2. In the making of a bag of the character described having a longitudinal seam and a bag bottom requiring transverse folds across the seam, the improved method of forming the longitudinal seam and of preventing failure in the same without delaying the completion of the bag, said method comprising forming the bag material into a bag tubing by overlapping the longitudinal edges and securing the same together by a film of slow-drying paste, arranging a binder strip for application longitudinally along the seam, having said binder strip of suflicient width to provide for overlying the outside surface of the bag tubin a substantial distance on both sides of said seam and having the underside of said binder strip covered with a quick-drying adhesive capable of forming an immediate strong bond between said strip and the surface of said bag tubing, positioning said binder strip on the surface of said said strip will overlie the surface on both sides of said sea/m, pressing said binder strip firmly against said surface, whereby said binder strip will cause said overlapping edges to act as a unitar structure during the folding of the bag bottom and prevent any movement of one edge with respect to the other pending the permanent setting" of said slower-drying film of paste.

3. In the making of a bag of the character described having a longitudinal seam and a bag bottom requiring transverse folds across the scam, the improved method of forming the longitudinal seam and of preventing failure in the same without delaying the completion of the bag, said method comprising arranging the bag material so that the longitudinal edges overlap at the seam and applying a film of ordinary slow-drying paste between the overlapped edges, arranging a binder strip for application longitudinally along the seam, having said binder strip of sufficient width to provide for overlying the outside surface 01' the bag a substantial distance on both sides of said seam and having the underside of said binder strip treated with a coating of glue and said glue allowed to dry, said glue having the property of drying quickly when moistened, moistening said glue immediately before applying said strip to the sufficiently to cause said glue to again, positioning said binder strip on the surface of said bag material so that said strip wil1 overlie the surface on both sides of said seam, pressing said binder strip firmly against said surface, and forming the bag bottom without waiting for said slower-drying film of paste between said overlapped edges of said bag material to "set," whereby said binder strip will cause said overlapping edges to act as a unitary structure during the folding of the bag bottom and prevent any movement of one edge with respect to the other pending the permanent "setting" of said slower-drying film of paste.

JAMES L. SHIVELY. 

